Clear, stable, dry-and-non-sticky antiperspirant (hereinafter AP) products have long been desired by consumers. Commercially available products today do not meet all of these four consumer desires. For example, water based clear AP products (e.g., simple aqueous solutions of active ingredients and water in silicone emulsions) generally feel wet during application and for a significant period of time thereafter. Another example, clear stick products (e.g., based on active dissolved in propylene glycol and Milithix thickeners) typically feel drier but are still too sticky to achieve broad consumer acceptance.
One known formulation approach for making clear, stable, dry-and-non-sticky feeling AP products is to combine a non-aqueous solution of AP active with a dry-feeling, low viscosity, non-polar silicone emollient. The silicone emollient will reduce the sticky feel of the active solution and impart a dry, lubricous feel to the product. However, use of this approach has been limited because of the incompatibility of the polar, non-aqueous solvents (e.g., diol) used to make solutions of antiperspirant actives and the non-polar silicone emollients.
There have been several ways to overcome this incompatibility presented in the literature. For example, U.S. Pat. No. 4,053,581 discloses the dissolving of an AP active and a non-polar silicone emollient (e.g., cyclomethicone) into an anhydrous ethanol. Another example, U.S. Pat. No. 6,485,715, discloses a method of dissolving an AP active in a long chain diol, and then using dimethyl ether as a propellant and coupler for combining the solubilized AP active and a non-polar silicone emollient. U.S. Pat. No. 5,968,489 discloses a method of using a polar silicone emollient (e.g., dimethiconol) as a coupler between a solubilized AP active (e.g., dissolved in a long chain diol) and a non-polar silicone emollient (e.g., cyclomethicone).
In an attempt to improve the method disclosed in U.S. Pat. No. 5,968,489, one skilled in the art might try using an alternative class of polar silicone emollients in place of dimethiconol. For instance, U.S. Pat. No. 5,084,577 discloses polar silicone emollients that would be sufficiently polar to be compatible with the solubilized AP active.
In another attempt to improve the method disclosed in U.S. Pat. No. 5,968,489, one skilled in the art might try using yet another alternative class of polar silicone emollients in place of dimethiconol, for instance, dimethicone copolyols. The term dimethicone copolyols describes a class of materials that comprise a silicone chain with attached polar side chains that are typically made of polymers of polyethylene, polypropylene, polybutylene or mixtures thereof. Dimethicone copolyols have a wide range of molecular weights, viscosities, and polarities thus making this class of compounds useful as surfactants, compatiblizers, and solvents in a wide variety of consumer products ranging from cosmetics to automotive waxes. However, one skilled in the art can not merely substitute a dimethicone copolyol for dimethiconol. In fact, doing so requires more than routine experimentation; such will be exemplified herein.
What is needed is a clear, stable, dry-and-non-sticky feeling anhydrous antiperspirant product based on a solution of an AP active and a select group of polar silicone emollients.